SMTP Relay Built for Developers. Trusted by Production Teams.

MailKai's SMTP Relay API delivers transactional and marketing emails with 99.9% uptime, pre-configured DKIM/SPF authentication, and a developer experience that makes integration effortless.

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5,000 Relays Included | Read API Docs

Relay Every Email. Miss No Inbox.

When your application sends a password reset, invoice, shipping notification, or two-factor authentication code, failure is not an option. MailKai's SMTP Relay API is engineered for exactly that standard — with redundant sending infrastructure, automatic retry logic, real-time delivery webhooks, and an SLA that backs up every promise with hard uptime guarantees.

Everything a Production Grade Relay Should Have

DKIM & SPF Pre-Configured

Your DNS setup is guided step-by-step at onboarding. DKIM signing and SPF alignment are automatically applied to every message, protecting your sender reputation from day one.

Multi-Port SMTP Support

Connect over port 25, 465 (SMTPS), or 587 (STARTTLS)  whichever your stack demands. Port blocking is never a sending problem on MailKai.

Dedicated & Shared IP Options

New senders start on our carefully managed shared IP pool. High-volume senders can upgrade to dedicated IPs with automated warm-up scheduling included.

Real-Time Webhooks

Receive instant HTTP callbacks for every delivery event sent, delivered, opened, clicked, bounced, or complained. Build reactive application logic without polling.

RESTful API & SDK Support

Send via SMTP or our RESTful HTTP API. Official SDKs available for Node.js, Python, PHP, Ruby, Go, and Java. A Postman collection is included for rapid testing.

Automatic Bounce Management

Hard and soft bounces are categorised, processed, and suppressed in real time. Never accidentally re-send to a bounced address and damage your reputation unnecessarily.

100M+ Global Suppression

Every outbound message is checked against our continuously updated global suppression database before transmission, eliminating invalid and complaint-generating addresses automatically.

99.9% Uptime SLA

Our infrastructure is built across redundant multi-region cloud nodes. Check live system status at status.mailkai.com and review our publicly posted historical uptime.

Integrate in Under 30 Minutes

What Our Customers Use the Relay API For

  • Transactional notifications — order confirmations, shipping updates, account activity alerts
  • Authentication emails — OTPs, password resets, two-factor authentication codes
  • SaaS product emails — trial expiration notices, billing receipts, feature onboarding
  • Healthcare and financial alerts — appointment reminders, balance alerts, compliance notices
  • High-volume batch sending — marketing blasts routed through API for maximum deliverability
  • White-label reseller infrastructure — agencies and platforms sending on behalf of clients

Pay Only for What You Send

FREE TRIAL

5,000 relays

Free 14 Days

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STARTER

Up to 250K/mo

$12/month

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GROWTH

Up to 1M/mo

$55/month

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BUSINESS

Up to 5M/mo

$149/month

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ENTERPRISE

Custom Volume

Contact Sales

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Buy SMTP Relay

MailKai’s SMTP Relay API delivers transactional and marketing emails with 99.9% uptime.

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